The invention relates to a locking device and a locking method for locking a tool to the tool holder of a rotary drilling rig.
Rotary drilling rigs are primarily used in civil engineering or in the search for mineral resources for the sinking of boreholes, in particular for producing cased boreholes.
When drilling holes, with many types of ground and many drilling methods (e.g. rotary drilling methods or oscillation drilling methods) the drilling tools need to be replaced frequently. In conventional drilling rigs the tool holder is located directly under a rotary drive for driving the drilling equipment. The drilling tools, particularly augers, drilling buckets or casings, are inserted into this tool holder, and locked after insertion. The rotary drive is often a top drive (KDK), which drives the push pipe or pipe string, and often both elements.
Particularly in the production of cased boreholes using rotary drilling rigs, a frequent tool change is needed, at least with respect to the casings, but also with regard to the excavating tools (for example, drilling augers or drilling buckets). When driving the casing, the soil and rock is first loosened with the excavation tool and removed, and, simultaneously or after fixed intervals, the casing is moved downwards in the hole by the push pipe. Depending on the ground conditions, a casing machine is used in addition.
For removing the excavated material from the borehole, it is necessary to disengage the casing from the push pipe, to pull out the Kelly bar along with the excavation tool, to deposit the excavated material next to the borehole, to insert the excavation tool back into the casing with the Kelly bar, and to lock the push pipe to the casing again.
Depending on the ground conditions, sometimes the excavating tool on the Kelly bar must also be replaced and locked.
If a new hole is dug and cased, the casing has to be lifted completely and transported to the borehole by the rotary drilling rig. In this process, casings and excavation tools are therefore temporarily guided freely suspended from the rotary drilling rig.
On being inserted, the drilling tools engage with an area of the tool holder, mostly with positive locking. For locking, locking pins are generally used, which are arranged in sleeves on the tool or the tool holder and which are displaced manually by a lever or by a hydraulic system, in order to engage in holes of the counterpart and thereby lock the latter.
A disadvantage of the prior art is that the known devices are comparatively complicated and thus expensive, and that their use is expensive, since the control lines and control elements must be guided through the rotary drive of the drilling rig into the rotating tool holder. In addition, integrated monitoring of the lock is very difficult or not possible at all, resulting in a deterioration of occupational safety.
European patent application publication EP 1 624 151 A2 describes an accommodation for a tubular drilling tool, which accommodation has a locking device comprising a radially arranged locking pin. The locking pin is rotatably and displaceably arranged in a sleeve. On the locking pin there is disposed a radially outwardly extending stud or guide pin that engages an elongated slot running helically in the sleeve. Through a rotary motion of the locking pin about its longitudinal axis the locking pin is displaced laterally, parallel to the longitudinal axis. The rotary motion of the pin relative to the sleeve is effected by a movement system, using an electric motor, for example. A position monitoring system for monitoring the position of the locking pin is not provided.